This invention relates to optical switches and more particularly to optical switches that utilize waveguides in an electro-optic medium.
One type of optical switch in the prior art is disclosed in U.S. Pat. No. 4,012,113 to H. W. Kogelnik and R. V. Schmidt entitled, "Adjustable Optical Switch or Modulator", and issued Mar. 15, 1977. In this Kogelnik et al patent two strip waveguides are formed in an electro-optic substrate and are positioned in the substrate such that the waveguides are parallel to each other and sufficiently close over an interaction length such that coupling is achieved from one waveguide to the other. At least two pairs of electrode elements are positioned proximate to the waveguides in the interaction length region such that opposite electric fields can be established in each of the two waveguides by applying opposite potentials across adjacent pairs of the electrode elements. Electric adjustability of both the crossover and straight-through states is achieved. This switch, however, is operated entirely in response to the potentials applied to the electrode elements and there is no suggestion in the Kogelnik et al patent as to how this switch can be operated in response to optical pulses within the optical pulse stream.
Optical switches or bistable elements that can be operated by optical pulses have been disclosed in the prior art using a variety of nonlinear optical materials within a Fabry-Perot resonator. One such device which has been recently disclosed uses an electro-optic medium within the Fabry-Perot cavity. See for example the article entitled, "A Bistable Fabry-Perot Resonator", by P. W. Smith and E. W. Turner, Applied Physics Letters, Vol. 30, Mar. 15, 1977, pages 280-281. In this latter device the optical energy present at the output of the cavity is caused to energize a photodetector whose output voltage is coupled back to electrode terminals that change the refractive index of the electro-optic medium. These devices that use a Fabry-Perot cavity suffer the disadvantage that they have only two ports and that any power not transmitted through the device is reflected and is difficult to use.